...this is particularly hilarious given that I've spent a week or so learning about modding the original Deus Ex, which added ladders to the Unreal Engine before it had any built-in support for them.
Textures in UE could be categorised in named groups. The Deus Ex team couldn't make the janky physics do it in any sensible way, but they could hack together a ladder-climbing movement mode, they could detect "player is standing near a wall", and they could ask "what is the name of the texture group, if any, that the texture on that wall belongs to?"
So you can climb any surface in Deus Ex whose texture has been filed in the "Ladders" group